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(No Model.)

B. D. ARNOLD.

HARROW DISK.

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EVERETT D. ARNOLD, OF TROY, NEW YORK, ASSIGNOR TO THE TROY STEEL ANDIRON COMPANY, OF SAME PLACE.

HARROW-DISK.

SPECIFICATION forming part of Letters Patent No. 488,514, dated December20, 1892.

. Application filed November 5, 1891- Serial No.410,970. (No model.)

To all whom it may concern.-

Be it known that I, EVERETT D. ARNOLD, a citizen of the United States,residing at Troy, county of Rensselaer, and State of New York, haveinvented certain new and useful Improvements in Harrow-Disks, of whichthe following is a specification.

My invention relates to such improvements and consists of the novelconstruction and combination of parts hereinafter described andsubsequently claimed.

Reference may be had to the accompanying drawings, and the letters ofreference marked thereon, which form a part of this specification.

Similar letters refer to similar parts in the several figures therein.

Figure 1 of the drawings is a plan View of the outer or convexed side ofmy improved barrow-disk. Fig. 2 is a plan View of the inner or concavedside of the same. Fig. 3 is a central cross-section of the same taken atthe broken line 33, in Fig. 1. Fig. at is a similar section of a portionof a plane disk after its peripheral edge has been hammered. Fig. 5 is asimilar section of a concavo-convex disk, after its peripheral edge hasbeen hammered on the convex side and before the edge has been ground onthe concave side. Fig. 6 is a similar section of a portion of aconcavo-convex disk having its peripheral edge hammered on the convexside and ground on the concave side. The last three figures are drawnupon an enlarged scale.

My invention relates to that class of metallic harrow-disks which aremade from a circular sheet or thin plate of wrought metal pressed intothe form of a concavo-convex disk and provided with a peripheral cuttingedge. The cutting edge has been formed heretofore by cutting grinding orrolling the peripheral edge of the disk, or by combining some of theseoperations.

Harrow-disks, when in use, are mounted upon a shaft that is so inclinedto the line of draft as to cause the individual disks to present theirconvex side to the front to engage the soil. The convex side istherefore the working side, the concave side serving to aid insupporting and strengthening the disk. It is desirable to make the partswhich directly engage the soil as hard as possible, without subjectingthem to the danger of chipping or breaking in stony ground.

I have ascertained that by hammering the peripheral portion of the diskon the convex side, or the side to be convexed, I am able to produce onthat side of the disk a very hard case or skin that will offer greatwearing resistance to the soil, which hardened ease extends over thewhole hammered surface and to the extreme cutting edge of the disk,while the other or concave sideis left comparatively soft and pliable, acondition well adapted to aid the hardened portion in withstandingshocks or blows, such as would break or chip a hard metal.

I am aware that castiron mold-boards for plows have been case-hardenedby chilling the casting, but the mold-boards of plows are not providedwith a cutting edge, and a castiron barrow-disk, if made strong enoughto be durable, would be too thick to readily pass through the soil andtoo heavy to be of practical use. Mold-boards have also been made ofhighly tempered steel welded upon iron strengthening plates. Such a formof construction is not adapted for earth-cutting blades for the reasonthat when the cutting edge of the blade should become partially Worn byuse, the support of the harder metal would be weakened so that thelatter would chip and break away, leaving a blunt edge. Defectivewelding would also cause the two metals to chip or scale off, one fromthe other. Whereas a hammer-hardened case on an integral disk of wroughtmetal is not sufficiently well defined and separated from the body partof the disk to chip or scale off, but Wears away gradually and evenlywith its underlying support, maintaining a sharp cutting edge as theperipheral parts wear away.

Harrow-disks are almost universally made of wrought metal and preferablyof rolled plates or sheets of low-carbon steel.

After many experiments, I am convinced that a hammer-hardened case isthe only successful shield which can be practically applied to thewearing parts of a wrought-metal barrow-disk. The hammer-hardened caseserves to materially increase the life of the disk and the efficiency ofits cutting edge.

The edge can be sharpened from time to time by bevel-grinding or cuttingthe softer side of the peripheral portion of the disk, which maintainsthe sharp cutting edge within the hammer-hardened case.

Referring to the drawings, Arepresents my improved disk, preferably cutfrom a sheet of rolled steel in any known manner adapted to give it acircular outline and an approximately plane surface. The disk is thenhammered, in a hot or cold condition, along its peripheral edge on oneside of the disk, until the beveled edge, B, is produced, and thedesired degree of hardness is imparted to the metal beneath the hammeredsurface. The disk is then convexed by suitable dies, in the usualmanner, so that the hammered surface is located on the convex side. Theedge on the concave side is then cut or ground in a lathe which reducesit from the blunt or dull condition shown in Fig. 5, to the sharpcutting edge shown in Fig. 6. The grinding or cutting process produces abeveled surface, 0, on the concave side of the disk along its periphery.

The disk is provided with a central aperture adapted to receive thesupporting shaft in the harrow.

The cutting edge'can be maintained in a sharp condition by applying fromtime to time, as required, the grinding or other process which cuts awaythe metal on the concave side of the disk.

The method of making barrow-disks herein shown and described, is notclaimed in this application, but is made the subject matter of, andclaimed in a separate application filed herewith.

What I claim as new and desire to secure by Letters Patent is 1. Aconcavo-convex barrow-disk provided with a peripheral cutting edge andcomposed of an integral plate of wrought metal, having a hammer-hardenedcase on the peripheral portion of the convex side of the disk,substantially as described.

2. A concavo-convex barrow-disk composed of an integral plate of wroughtmetal having its peripheral portion hammer-hardened on the convex sideof the disk, and bevel 5c ground or cut on the concave side of the disk,whereby the peripheral portion of the disk is provided with ahammer-hardened case on the convex side of the disk, and with acutt-ingedge on the peripheral edge of the hardened case, substantially asdescribed.

In testimony whereof I have hereunto set my hand this 28th day ofOctober, 1891.

E. D. ARNOLD.

\Vitnesses:

GEO. A. MOSHER, FRANK 0. (loans.

